The invention relates to a vehicle energy supply system.
The conventional energy supply systems in motor vehicles usually comprise a generator, a (starter) battery, a plurality of consumers, and components for distributing the electric energy.
The generator feeds, as a function of the principle, a pulse-shaped current or rather a current with an alternating component into the energy supply system of the vehicle. In this context, the frequency and the amplitude of the alternating component depends, inter alia, on the direct component of the current and the design, as well as the rotational speed of the generator. A variation in voltage—the so-called generator ripple or the vehicle's electrical system ripple—is generated, as a function of the output impedance of the generator or rather the vehicle's electrical system impedance, at the terminals of the generator or rather the vehicle's electrical system. The generator ripple results in more stringent requirements on the design of specific components of the consumers or in restrictions on the connection possibilities of the consumers to the electrical system of the vehicle.
In order to feed specific consumers, such as the electric steering system, it is logical to increase its supply voltage in relation to the voltage of the vehicle's electrical system or to uncouple its feed from the vehicle's main electrical system into a dedicated branch of the vehicle's electrical system. In order to increase the supply voltage for specific consumers or in order to feed specific consumers in an uncoupled branch of the vehicle's electrical system, direct voltage transformers are usually used. Direct voltage transformers are technically complex and usually constitute an electromagnetic compatibility [EMC] risk and an enormous cost factor.
An object of the invention is to provide a vehicle energy supply system that has been improved over the prior art.
This and other objects are achieved by an energy supply system of the vehicle including a first branch of the vehicle's electrical system and a second branch of the vehicle's electrical system. The first branch of the vehicle's electrical system and the second branch of the vehicle's electrical system are coupled together by means of an energy transfer device. The energy transfer device is designed in such a manner that energy is drawn from the alternating component of the voltage in the first branch of the vehicle's electrical system by means of the energy transfer device and is then fed to the second branch of the vehicle's electrical system.
Basically the invention utilizes with simple means a spurious effect (actually noise), that is, the alternating component of the voltage in the first branch of the vehicle's electrical system, in order to supply a second branch of the vehicle's electrical system with energy, preferably on a different voltage level. In this way the goal is achieved that the alternating component of the voltage in the first branch of the vehicle's electrical system is reduced with simple means. This strategy has a positive effect on the service life of the components in the input circuits of the electrical consumers in the first branch of the vehicle's electrical system. The input sided control of the supply voltage for these consumers is simplified. The components in the input circuits of the electric consumers in the first branch of the vehicle's electrical system can be dimensioned smaller, thus producing weight and cost advantages. In addition, multi-voltage vehicle electrical systems with a freely selectable reference potential can be realized in a simple way without the use of a switching direct voltage transformer.
A further development of the invention provides that the first branch of the vehicle's electrical system comprises a first energy accumulator, a feed unit and/or a consumer.
An alternative or additional further development of the invention provides that the second branch of the vehicle's electrical system comprises a second consumer and/or a second energy accumulator.
The feed unit and/or the first consumer comprises (comprise) preferably an electric machine, by means of which the alternating component of the voltage or a voltage ripple in the first branch of the vehicle's electrical system is generated.
The energy transfer device comprises preferably a coupling unit, in particular a capacitor, by means of which the energy transfer device is coupled with respect to an alternating voltage to the first branch of the vehicle's electrical system.
The energy transfer device comprises preferably a transfer unit, in particular a transformer, by means of which the energy of the alternating component of the voltage is transferred from the first branch of the vehicle's electrical system into the second branch of the vehicle's electrical system, which exhibits, in particular, a voltage level that is different from the voltage level of the first branch of the vehicle's electrical system.
The energy transfer device comprises preferably a rectifier, which comprises, in particular, semiconductor elements, like diodes or transistors. The rectifier rectifies, in particular, the current pulses or voltage pulses that are transferred by the transfer unit.
Preferably the amplitude of the alternating component is reduced by taking the energy from the alternating component of the voltage in the first branch of the vehicle's electrical system, and, thus, the vehicle's electrical system ripple in the first branch of the vehicle's electrical system is damped.
Preferably a capacitor of the coupling unit forms with the line inductance, the primary sided inductance of the transfer unit, or an inductance L, which is connected in series with the capacitor, an LC resonant circuit, which is excited by the vehicle's electrical system ripple. Thus, the energy flow from the first branch of the vehicle's electrical system into the second branch of the vehicle's electrical system can be controlled or optimized.
The resonant frequency of the LC resonant circuit is designed so as to be variable, preferably based on a controlled change in the capacitance value of the capacitor and/or in the inductance value of the inductance.
Preferably the capacitance value of the capacitor can be varied in discrete stages by connecting or bridging individual or multiple capacitors.
The inductance value of the inductance is preferably adjustable by means of a coupled inductance and a biasing of the core material of the coupled inductance. The inductance, which is connected in series to the energy transfer device, is usually designed in an advantageous manner with a small number of turns (typically >10) on a core material. With an additional inductance (control inductance) having a higher number of turns (for example, >100 turns) on the core material, the core material can be highly biased by means of a relatively low current in the control inductance (mA range). Since the inductance is a function of the biasing (for example, in the range of the saturation limit of the core material), it is possible to adjust specifically the primary sided inductance value with the control inductance.
In order to control and regulate the energy flow, the resistors in the energy transfer device are preferably variable. The resistors can be connected in series to the capacitances, inductances as well as the transformers as discrete components in the energy transfer device. To this end, adjustable resistors and/or switchable or rather bridgeable resistors can be used in an advantageous manner.
In order to control and/or switch off the energy flow from the first branch of the vehicle's electrical system into the second branch of the vehicle's electrical system, a supply line between the energy transfer device and the first branch of the vehicle's electrical system or the second branch of the vehicle's electrical system is designed so as to be interruptable, for example, by means of a switching device. It is also possible to carry out in an advantageous manner an energy flow control or switch off process by changing the LC resonant frequency in the energy transfer device in such a manner that the resonant frequency of the energy transfer device is adjusted to a frequency range, in which there is no ripple or just a slight ripple in the vehicle's electrical system.
An especially preferred embodiment provides that several energy transfer devices are connected in parallel. In this case the capacitance value of the capacitors and/or the inductance value of the inductances is (are) adjusted by regarding a first energy transfer device as the reference system (observer system) and by adjusting the second energy transfer device in such a manner that the result is an improved energy transfer response of the second energy transfer device relative to the reference system. At this point the teaching, disclosed in the German patent application 102007050228.3, can be applied analogously. By using an energy transfer device (a path) as the reference system or the observer system, it is possible to optimize the parameters (inductance values, capacitance values, resistor values and/or the desired values for the current sources and the voltage sources) in the other paths.
A further development provides that in order to control and/or switch off the energy flow from the first branch of the vehicle's electrical system into the second branch of the vehicle's electrical system, a supply line between the energy transfer device and the first branch of the vehicle's electrical system or the second branch of the vehicle's electrical system is designed so as to be interruptable, for example, by means of a switching device.
It is provided preferably that the voltage levels of the first branch and the second branch of the vehicle's electrical system are different, so that, for example, a first branch of the vehicle's electrical system can be designed as the vehicle's high voltage electrical system, and a second branch of the vehicle's electrical system can be designed as the vehicle's low voltage electrical system.
A preferred embodiment provides that a switching element is integrated into the energy transfer device. This switching element generates by periodic switching an alternating component. It is also possible with this switching element to generate an alternating component in the energy transfer device in situations, in which there is no ripple in the vehicle's electrical system, so that this energy can be transferred from the first branch to the second branch of the vehicle's electrical system.
In addition, the first branch and the second branch of the vehicle's electrical system are energetically connected preferably by means of a DC/DC converter, in particular, a unidirectional DC/DC converter.
The second branch of the vehicle's electrical system exhibits preferably no energy accumulator. Then the electrical consumer in the second branch of the vehicle's electrical system is supplied directly, preferably with a higher voltage than in the first branch of the vehicle's electrical system.
The invention is explained in detail below by means of examples with reference to the following figures.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
Identical reference numerals denote the same or corresponding components in the different figures.